The 6.5L and the Caterpillar 3116 are equipped with a starter motor relay. The relay is located in the rear of the vehicle on the right-hand side of the engine.

In order to prevent the engine from starting while performing these checks, disconnect the electrical connector at the fuel shutoff solenoid.

1. Disconnect the negative battery cable. Refer to

   Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

   in General Information.
2. Disconnect the electrical connector from the starter relay.
3. Connect jumper wires from terminals A, D, E and F in the connector to the relay.
4. Reconnect the negative battery cable.
5. Connect a circuit powered test lamp to the negative battery terminal.
6. Probe the red wire terminal (A and E) connector. The lamp should light since the red wire should be hot at all times. If the lamp does not light, check the circuit.
7. Turn the ignition switch ON, but do not crank the engine. The red wire terminal should be hot, but not the purple wire or the purple/white terminals.
8. Crank the engine while checking the red, purple and purple/white wire terminals. The test lamp should light.
9. Probe the purple wire at the starter while cranking the engine. The test lamp should turn on. Turn the ignition switch off.
10. Check for continuity between connector terminal F and the ground with a digital multimeter with the ignition OFF. The reading should be zero. The relay is grounded through the engine wiring harness to the engine block.
11. If power is reaching the relay and the continuity check is OK but the engine will not crank, replace the relay.

The engine is equipped with optional overcrank protection. The thermostat should be checked before replacing the relay.